Cutting head for dry shaving razors



y 24, 1951 v. KOBLER ET AL 2,562,104

CUTTING HEAD FOR DRY SHAVING RAZORS Filed Feb. 20, 1948 4 A H55 2 Z2 I Patented July 24, 1951 2,562,104. cu'if'lfnsd Eon nRY SHAVING RAZORS Victor-Koblerand Werner Kobler, Zurich, Switzerland Application, February 20, 1948,; Serial No. 9,836

n ..w .a d to 1 .38

Section r, Public at 690, August 8, 1946 Bate texnim o er 7, 19,59

The p esen i vent n re ates t a cu t head for dry shav n azors. ompri n a r gid ho l w ter knife. and a rec cally ma ble nner k ife. m un d n t e o yni t- I Que. o he o j cts of theinventi n is o odues a cutt n sd o th ype re e r d to bove which is so designed as to ODGI'MQ smoothly a d to permit a close shave. To this end the cooperatingspaeed cuttingfaces of both knives are convex curved in their longitudinal direction, 1. e. along the direction in, which the inner knife reciproc tes an are roof haped inthe tra svers direction to that longitudinal direction, that'is, a mposed cf w facets r g d a a large obtuse angle and intersecting at'a medial line so as to: provide an edge or ridge which foreesthe skin to. change its an le. in h shav op ration- This design of the cutting faces permits to obtain the fo lowin ad an a s v c n u tin 111 h ch are strai ht in. thei n itudina direction and flat or rounded the transverse direction:

This curvature allows a better and cleaner shave because the skin. is automatically stretched by the curvature of the cutting surface. Whilst with straight cutting surfaces both outer ends of the cutting face rest on the skin this causing unpleasant pressure, with the longitudinally curved cutting face according to the invention the maximum pressure is concentrated in the centre portion of the cutting face, the ends of the latter rest on the skin with but slight pressure, thus causing no pain. Moreover, the lengthwise outwardly curved cutting head allows concave parts of the skinto be cleanly shaved.

Further features and advantages of the novel cutting head will be pointed out in the following description of an embodiment of the invention which is illustrated by way of example in the accompanying drawing, in which Fig. l is a perspective view of the cutting head,

Fig. 2 is a perspective view of the inner knife,

Fig. 3 is a cross-section of the cutting head.

Fig. 4 is a longitudinal section showing the cutting head and the fastening and driving means for the latter and the top part of the casing.

Figs. 5-8 show diagrammatically cutting surfaces which are roof-shaped and rounded in cross-section and serve for explaining the advantages of the former over the latter.

Referring now to Figs. 1-3 of the drawing I denotes the hollow outer knife, in which the inner knife 4 is inserted. The cutting surface 2 of the outer knife is outwardly curved in the longitudinal direction and is composed of two facets archin reo-43) ranged at a large obtuse angle so, as to intersect a o e a l n di al med a e. or n edge and, thus, may be described as roof-shaped in the transverse direction. The medial edge or ridge of the cutting surface 2 functions as a comb, the teeth of which are separated by spaces 3, through which the hairs to be cut enter the interiorof the hollow outer knife and are cut by the teeth 5 of the inner knife 4, reciprocating in the lon tu in dire one' t th 5 a p: arated by spaces 6., The teeth of the cutting faee of the outer knife are rounded off at their ends and project somewhat beyond the side walls f e O er kni e as. indicated by numeral '1 hu fa i it tin the ent ance o he hair n o the spaces 3.

{The cutting face of the inner knife 4 is also wnvex hamd lon itudina ly t is, in he moving direction of the inner knife, and roofhaped n t t ansv s di e t o im r to th ex ior a d nter or su ac o he o r cu -The ut in fac of the nn r kn e is a i n fit on the cutting face of the outer knife and, on the one hand, is guided in its position by the apex o t e of shan d n eri r sur ace s yt lengthwise curvature, and, on the other handby a groove 8 in the bottom part 9 of the outer knife.

Two bolts ID with grooves ll, arranged in the bottom piece 9 of the outer knife, serve to fasten the cutting head to a housing (Fig. 4) of a dry shaving razor by means of the pawls l2 which, on setting the cutting head, clinch in the grooves I I. The reciprocally moved clapper l3, driven by an electric motor or similar device, is pivoted on an axle pin centrally fitted in the curvature of both cutting surfaces of the cutting head. On the upper free end, the clapper is provided with a small cap l5 which is pressed towards the inner cutting comb by means of the spring [6, thus effecting an elastic impinging of the inner knife on the outer knife. The cap l5 of the clapper l3 engages the slot 1 of the inner knife, thus when oscillating the clapper I3 the inner knife is similarly moved so that the hairs, on entering the cutting spaces of both knives, are then effectively cut. Owing to the arc-like shape of the cutting surfaces, the inner knife moves oscillatorily around the center of the arc, the same serving simultaneously as the axle for the clapper, thus causing the distance between the carrier space 1 and the axle point I4 to remain identical in all moving positions. Thus, the tension of the spring l6 remains invariably the same so that an equal spring pressure is always assured. This also applies practically to embodiments in which the axle point is arranged slightly outside the arc-centre.

It is expedient to choose as large a radius as possible for the cutting surfaces of the cuttin head, for instance, from 50 to 200 mm, but at least about 30 mm., as round cutting surfaces with a smaller radius do not rest entirely in their whole length on the skin to be shaved thus rendering the shaving of convex skin surfaces more difficult.

Fig. 5 shows diagrammatically in cross-section a shaving head with a roof-shaped cutting face and Fig. 6 for sake of comparison a shaving head with a rounded cutting face. Both cutting heads being applied at right angles to the skin 20. With the same deflection T of the skin in the vertical direction the breadth B, on which the shaving takes place when the razor is moved in the direction of the arrow indicated, is much smaller with the roof-shaped cutting face (Fig. 5) than with the rounded cutting face (Fig. 6). The important advantage results thereby that in the first case the inner knife can be much narrower than in the second case, this again means less friction. Moreover with rounded cutting faces the inner knife must be made much wider because a narrow inner knife has no good guidance in the outer knife, whereas with the roof-shaped cutting faces the guidance is perfect. The concentration of the cutting action in the middle portion of the roof-shape in combination with the small inner knife provides a comparatively long way for the hairs to enter into the spaces 3 and facilitates the entering and permits to make the spaces narrow, thus causing less irritation of the skin.

As shown in Figs. 7 and 8 the roof-shaped cutting face (Fig. 7) is also advantageous over the rounded shape (Fig. 8) if the cutting head is guided over the skin to be shaved in a slightly slanting position in as much as the danger of the hairs being bent is much greater in the second case than in the first.

We claim:

A shear head for a dry shaver having in combination, a hollow outer cutter member having an outer surface for engaging the skin during shaving which surface is convexly curved in its longitudinal direction and is composed of two facets arranged at a large obtuse angle and intersecting along a medial longitudinal line, thus forming an edge for engagement with the skin to be shaved, at which edge the skin is forced to change its angle, said outer cutter having a plurality of slots extending transversely of its longitudinal extent, and opening to its hollow interior, the inner surface of said outer member opposite the skin engaging surface being curved longitudinally similarly to the outside and also being composed of two obtusely intersecting facets which form a line at their intersection, and a longitudinally reciprocable inner cutter located within the hollow of the outer cutter and having an outer surface conforming in shape to the inner surface of the outer member opposite the skin-engaging surface and having teeth with spaces therebetween, said inner cutter having less width than the interior intersecting facets so as to have free side edges, and a spring for pressing the inner cutter against said interior intersecting facets so that the inner cutter is guided by the apex of the intersecting facets.

VICTOR KOBLER. WERNER 'KOBLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date Germany Aug; 27,1937 

